1. Field of the Invention
The present invention relates generally to the field of electromagnetic devices for completing and interrupting current carrying paths between a source of electrical power and a load. More particularly, the invention relates to a novel technique for forming an electromagnetic operator which serves to complete and interrupt the current carrying paths in such devices upon the application or removal of control signals.
2. Description of the Related Art
A wide variety of electromagnetic devices have been devised for completing and interrupting current carrying paths between electrical sources and loads. In several families of such devices an electromagnet is formed by winding a conductive wire around a core. A field is generated by the electromagnet upon application of a current through the winding. The field is used to attract an armature which, in turn, causes displacement of movable contacts within the device. Depending upon whether the device is coupled in a normally open or normally closed orientation, the control signals may thereby complete a current carrying path through the device, or interrupt the path. Upon removal of the control signal from the actuator coil, biasing members such as compression springs are often employed to return the armature and movable contacts to their normal or biased position.
While devices of the type described above are generally suitable for many applications, they often include a large number of individual parts which must be separately designed, manufactured and assembled. For example, in a conventional contactor, an operator assembly, including the electromagnet coil is assembled around the coil or the coil bobbin in one portion of the contactor, while stationary and movable contacts are assembled in another portion of the device. Even in relatively small, single-phase devices, the resulting number of individual parts is fairly large. In larger, multi-phase devices, the number and size of the individual components is substantially increased, although certain components may be shared between power phase sections. As the number and complexity of the individual components of these devices increases, so does the cost both in terms of design, manufacturing, tooling, and assembly. Moreover, an increased complexity of the device sometimes gives rise to an increased risk of failure of individual components or subsystems which can reduce the useful life of the entire device package.
There is a continuing need, therefore, for an improved operator structure that can be used in electromagnetically-operated devices, such as contactors, circuit interrupters, switch gear, motor starters, and so forth. There is a particular need for relatively simple structures which can be manufactured of readily available materials and which is extremely robust. Such improved structures are advantageously actuated and returned to a normal position by means which do not require excessive power input as control signals.
The present invention provides a novel technique for forming an electromagnetic operator designed to respond to these needs. The structure incorporates an electromagnet assembly which is operative to draw an armature by virtue of an electromagnetic field created upon the application of control signals. The electromagnetic coil assembly is positioned in a plate-like structure, as is the armature. The plates are positioned in a mutually facing relation and the armature is held in a space relation with respect to the coil assembly by a lever-type pivot arrangement. In a preferred configuration, the pivot arrangement forms a fulcrum between the plate structures, and a generally C-shaped biasing spring urges the two plates away from each other in the normal condition. Upon energization of the coil assembly, the biasing force is overcome and the plates approach one another under the influence of the attraction of the armature in the resulting magnetic field. One or both of the plates may carry one or more contact members. In a presently preferred configuration, several such contact members are carried by one of the plates and complete contact when the two plates are moved toward one another. The plates may be made of a very robust, readily available material such as multi-layer laminate comprising a fiberglass and epoxy structure, such as materials used for the fabrication of circuit boards. The subassemblies of the operator are preformed and may be simply and easily mounted to one another in efficient assembly steps.